My suggestions.
1. Rain effect on windscreen.
2. It appears every airport I land at has a ramp handler called Heinrich, unless he stows away in the baggage compartment.
3. OAT gauge to detect possible icing.
4. Visual icing on wings, struts etc.
5. Animated passengers.
6. In the Payload Manager, a button to de-board passengers. I can not get them off the aircraft.
That's all for now after just one flight. I'm sure more to come once I get more familiar.

Hi Ian,
Welcome to the forum and thank you for your suggestions!
1. Rain effects
I agree, that would be an amazing addition to the add-on. I did have a look at the SDK A2A kindly provided for their rain effect, hoping to implement it at some point. But there's a little problem with their system: it doesn't allow for windscreen wipers! In other words: if I go for the A2A effect, I'd need to remove the wipers or render them useless. The only solution would be for me to come up with my own rain-rendering effect, and I think right now my time is needed elsewhere. I do see this as a possible update for the future though, but that would be way after the full release. I hope you understand.

3. Aye! I agree. We had a conversation about the OAT somewhere else in the forum already and my reason why it should be there is to determine your true airspeed! I know Wiley Post had one in his Vega, but I couldn't find one in any of the cockpit photos I got of regular Vegas. But I think this is too important to leave out. When I get to it, I'll include an OAT if I find an empty spot on the dashboard

4. Icing effects
I had those on my list very early on, but I don't think I'll implement proper structural icing in the Vega, simply due to time constraints.

5. Passengers
Yes, those will come in the full release!

6. Un-Boarding/Un-Loading
The idea of the passenger interface was that you click on the seat to toggle it's state. Empty seat means no passenger on the seat, blue man means someone is currently sitting there and yellow man means to toggle between those two states. Let's say you have a passenger sitting on seat 1L (blue), you click the seat and it turns yellow, indicating that this state will CHANGE. When you press the boarding button, any seat with a yellow dude will toggle its state, so if it was previously occupied, the passenger will leave the seat. If the seat was empty, it will get occupied. A similar logic applies to the cargo. You select what you want and then press the "load cargo" button, if your selection was "0 kg", then Heinrich will unload all your luggage.
After watching Peter's live-stream, and seeing how he couldn't work out the logic behind it, I know something needs to change to make this more clear. The question is HOW. I already changed some logic behind Heinrichs interaction, with version 0.90, he'll detect whether or not passengers are embarking or disembarking and announce it accordingly, and the same goes for the cargo. My suggestion is that I change the buttons to read "embarkdisembark passengers" and "load/unload cargo". This might clear up the miscommunication a little bit. The question is if I should add some sort of marking to the passengers as well?

So thanks again for your suggestions and thank you for supporting the project!

Just purchased the ATSimulations Antonov An-2...it has the A2A rain and working wipers...and they actually wipe the drops off the windscreen. So there must be a way to do it. I did see where Lewis at A2A offered to help you with this. How great...rain and wipers and sound (no sound on the An-2)...Wow!